Habitat Restoration Strategies Research Articles

Effects of patch size, disturbances on diversity and structural traits of tropical semi-evergreen forest in the lowland Indo Burma hotspot: implication on conservation of the threatened tree species

Information on geographic distribution, population and threat status of most globally red listed species in the Indo Burma zone are inadequate. Given the increase in the prevalence of isolated forest patches in the part of this hotspot, evaluation is necessary on how size of the remnant forest patches and on-going disturbances affects structure and diversity of remaining habitats including the population of some globally threatened tree species. Quantitative vegetation inventory by 500 m long and 10 m wide (0.5 ha) line transects were randomly set in nine fragmented tropical semi-evergreen forest patches in Tripura, Northeast India. The studied forests patches grouped into small, medium and large based on their respected sizes. Spatial variability was analysed in woody species diversity and structure along the patch size gradients and their response to both patch size and anthropogenic disturbances. Out of 167 species, 13 identified as red-listed species by IUCN under the present inventory. Most of the diversity and structural parameters showed statistically significant positive response with the forest patch size, except for stand dominance, disturbance, sapling density and number of aggregated distribution pattern decreased when patch size increased. In addition, most of the diversity and structural attributes showed negative response with disturbances. Present baseline data would serve as an effective tool for management and protection of this important forest type. Future habitat restoration programme and strategies for relocation of additional population and re-introduction of those globally threatened trees are recommended.

Edaphic niches of metallophytes from southeastern Democratic Republic of Congo: Implications for post-mining restoration

In southeastern D. R. Congo, about 550 metallophytes grow on soils with high copper and cobalt concentrations, 57 of which are endemics to these metalliferous environments. About 70% of those endemics are considered threatened by destruction of habitats through mining activities. To provide guidelines for future restoration programs, the edaphic ecological niches of eight endemic metallophytes (i.e. copper endemics) were studied using a pragmatic sampling method adapted for urgent conservation needs. Niches were modelled using violin plot along Cu, Co and C:N gradients representing the two main independent edaphic gradients among nine edaphic variables (C, N, C:N, K, P, pH, Co, Cu, and Mn). Copper endemics presented distinct edaphic niches along the copper and cobalt gradients, but differentiation was lower along the C:N gradient. In addition, edaphic elements presented covariations among them and metalliferous soils had higher nutrient and element content compared to the non-metalliferous soils of the region dominated by the Miombo woodland. The complexity of the soil composition and the edaphic niches of copper endemics revealed an important challenge in the implementation of the species conservation and the habitat restoration strategies of post-mining sites.

Softening the agricultural matrix: a novel agri‐environment scheme that balances habitat restoration and livestock grazing

The loss and degradation of woody vegetation in the agricultural matrix represents a key threat to biodiversity. Strategies for habitat restoration in these landscapes should maximize the biodiversity benefit for each dollar spent in order to achieve the greatest conservation outcomes with scarce funding. To be effective at scale, such strategies also need to account for the opportunity cost of restoration to the farmer. Here, we critique the Whole‐of‐Paddock Rehabilitation program, a novel agri‐environment scheme which seeks to provide a cost‐effective strategy for balancing habitat restoration and livestock grazing. The scheme involves the revegetation of large (minimum 10 ha) fields, designed to maximize biodiversity benefits and minimize costs while allowing for continued agricultural production. The objectives and design of the scheme are outlined, biodiversity and production benefits are discussed, and we contrast its cost‐effectiveness with alternative habitat restoration strategies. Our analysis indicates that this scheme achieves greater restoration outcomes at approximately half the cost of windbreak‐style plantings, the prevailing planting configuration in southeastern Australia, largely due to a focus on larger fields, and the avoidance of fencing costs through the use of existing farm configuration and infrastructure. This emphasis on cost‐effectiveness, the offsetting of opportunity costs through incentive payments, and the use of a planting design that seeks to maximize biodiversity benefits while achieving production benefits to the farmer, has the potential to achieve conservation in productive parts of the agricultural landscape that have traditionally been “off limits” to conservation.

Advancing the science and management of flats fisheries for bonefish, tarpon, and permit

The fish of the sub-tropical and tropical flats including bonefish (Albula spp.), Atlantic tarpon (Megalops atlanticus), and permit (Trachinotus falcatus), capture the imagination of specialized coastal marine recreational anglers. Until recently, little was known about the biology and natural history of these iconic species. Flats ecosystems are under threat from coastal development and environmental change while basic information on demographics and population size is lacking. This makes it difficult to understand the consequences of these threats, or to formulate potential management strategies. Through extensive partnerships involving anglers, industry, conservation organizations, natural resource agencies, and academics, the mysteries surrounding these species are starting to be solved. Nonetheless, many challenges remain. The systematics of these fish is complex, particularly for the bonefish which include a number of cryptic species. Identifying the timing and habitats associated with reproduction remain high priority such that management efforts can target protecting that important life-history event. Information on the spatial ecology of flats fish at various spatial scales is being elucidated by electronic tagging studies and angler tagging programs. Habitat science for these fish continues to improve but there is still need to identify effective habitat restoration strategies. Catch-and-release science has improved dramatically (especially for A. vulpes in The Bahamas) although there is need to for additional work across regions and species. Targeted species-specific management strategies (e.g., catch-and-release regulations) as well as more ecosystem-level strategies (e.g., habitat protection and fishing effort management) are increasingly being used for active management of flats fish and their habitats. Partnerships will remain key to addressing outstanding research questions and in working cooperatively to ensure that evidence (both scientific and stakeholder knowledge) forms the basis for management decisions.

A multiple habitat restoration strategy in a semi-enclosed Florida embayment, combining hydrologic restoration, mangrove propagule plantings and oyster substrate additions

Abstract Habitat loss and disturbance are ranked globally as the greatest threats to biodiversity. Development and coastal population growth are the leading causes for habitat losses. Recently, the restoration of marine habitats has increased, especially with the goal of increasing non-consumptive ecosystem services derived from mangrove and submerged aquatic vegetation (SAV) along with biogenic oyster reefs. Habitats reside in landscapes dominated by multiple species. Rather than focusing on a single habitat such as oysters or mangroves or SAV, we took an approach restoring multiple adjacent habitats to accelerate restoration in a Florida embayment that had been significantly degraded prior to the restoration of natural tidally generated flows. After a multiple habitat die-off, a project was initiated in 2006 to reintroduce tidal flushing. The re-introduction of tidal flushing, however, did not result in immediate recovery of mangrove shorelines or oyster-dominated reefs. There was a lack of mangrove propagule production and significant substrate limitation in areas with appropriate salinity, sediment and tidal flows. From 2009–2012, red mangrove (Rhizophora mangle) propagules were collected (over 500,000) and planted for a total area of 3.24 ha. From 2009–2010, five intertidal reefs were constructed by adding bagged and fossil shell (54 MT) for Crassostrea virginica larvae to recruit onto totaling over 779 m2. Monitoring of planted mangrove versus unplanted shorelines demonstrated that prop root and drop root densities were higher where propagules were planted (28 m−2) versus unplanted (2.3 m−2). Oyster densities and mean sizes (multiple year classes) at new and natural reefs were measured after 8, 12, and 24, and 36 months. An initial settlement pulse was observed in the first 8 months followed by an increase in the density of greater than 1-year old oysters. Xanthid crab densities (Eurypanopeus depressus and Panopeus spp.) in restored reefs and natural reefs were similar, while Petrolisthes armatus densities were lower in restored reefs. Whole reef seston filtration rates over restored reefs were −26 to 157 L m−2 h−1 when measured at 4, 15, 28, and 40 months. A multiple habitat approach may be useful in accelerating the natural ecological succession, especially if the project site has reached a degraded, alternate ecological state. These results suggest a multiple habitat approach can be useful in providing non-provisioning ecosystem services to a Florida embayment.

Diagnostic model construction and example analysis of habitat degradation in enclosed bay: III. Sansha Bay habitat restoration strategy

Unbalanced inputs and outputs of material are the root cause of habitat degradation in Sansha Bay, Fujian Province, China. However, the cumulative pollution varies in different geographic locations and natural conditions in the enclosed bay. In this study, hydrodynamic conditions, sediment characteristics, and aquaculture methods were recognized as the underlying causes of spatial heterogeneity in the distribution of nitrogen and phosphorous pollutants, the two major controlling factors of habitat degradation in the bay area. In order to achieve the goal of balancing nutrient inputs and outputs in Sansha Bay, we developed a feasible and practical zone restoration strategy for reasonable adjustment and arrangement of aquaculture species and production scale in accordance with varying hydrodynamic conditions and sediment characteristics in six sub-bay areas (sub-systems). The proposed zone restoration strategy lays a solid foundation for habitat restoration and management in Sansha Bay.

Beneficial insects attracted to native flowering buckwheats (Eriogonum Michx) in central Washington.

Native plant and beneficial insect associations are relatively unstudied yet are important in native habitat restoration programs aimed at improving conservation biological control in perennial crops such as wine grapes. Beneficial insects (predators, parasitoids, pollinators) attracted to 10 species of flowering native wild buckwheat (Eriogonum spp.) in central Washington were identified and counted on transparent sticky traps. Combining all categories of beneficial insects, the mean number per trap ranged from 48.5 (Eriogonum umbellatum) to 167.7 (Eriogonum elatum). Three Eriogonum spp. (E. elatum, Eriogonum compositum, and Eriogonum niveum) attracted significantly more beneficial insects than the lowest-ranked species. E. niveum attracted greatest numbers of bees and parasitic wasps, and E. elatum was highly attractive to predatory true bugs and beneficial flies. Blooming periods of Eriogonum spp. extended from mid April to the end of September. This study demonstrates the attraction of beneficial insects to native flowering buckwheats and suggests their potential as a component of habitat restoration strategies to improve and sustain conservation biological control in Washington viticulture.

Using spatially-explicit population models to evaluate habitat restoration plans for the San Diego cactus wren (Campylorhynchus brunneicapillus sandiegensis)

A long-standing debate within conservation is how best to allocate limited management resources: should reserve area be increased, should anthropogenic disturbances be mitigated, or should connectivity be increased? We explore these issues for the San Diego cactus wren, a California Species of Special Concern. To assess the relative benefit of different post-fire habitat restoration strategies, we forecasted wren abundance over the next 100years under three restoration strategies: (i) create new “stepping stone” habitat patches to form corridors which connect existing patches, (ii) augment existing habitat patches, and (iii) create new habitat patches in areas with low fire risk. We considered both small-scale and large-scale restoration efforts of 20 and 200ha of habitat, respectively. To forecast wren abundance, we used a meta-population model created from maps of wren abundance, cactus abundance, land use, and estimated fire probability. Estimates of fire probability were obtained by relating previous fire locations to environmental variables and human population density. Results indicate that the best management strategy for a 20-ha restoration effort is to augment habitat in patches habitable for wrens, and that the best strategy for 180ha of additional restoration (or 200 total hectares) is to improve wren dispersal via new corridors. Results also indicate that there is no decline in long-term wren abundance caused by planning the first 20ha of restoration separately from planning a subsequent 180ha. Our modeling approach provides insight into the relative benefit of several realistic restoration scenarios, providing an important tool for species conservation and habitat restoration on complex landscapes.

Spatial Extent and Dynamics of Dam Impacts on Tropical Island Freshwater Fish Assemblages

Habitat connectivity is vital to the persistence of migratory fishes. Native tropical island stream fish assemblages composed of diadromous species require intact corridors between ocean and riverine habitats. High dams block fish migration, but low-head artificial barriers are more widespread and are rarely assessed for impacts. Among all 46 drainages in Puerto Rico, we identified and surveyed 335 artificial barriers that hinder fish migration to 74.5% of the upstream habitat. We also surveyed occupancy of native diadromous fishes (Anguillidae, Eleotridae, Gobiidae, and Mugilidae) in 118 river reaches. Occupancy models demonstrated that barriers 2 meters (m) high restricted nongoby fish migration and extirpated those fish upstream of 4-m barriers. Gobies are adapted to climbing and are restricted by 12-m barriers and extirpated upstream of 32-m barriers. Our findings quantitatively illustrate the extensive impact of low-head structures on island stream fauna and provide guidance for natural resource management, habitat restoration, and water development strategies.

Effectiveness of intervention methods against crop-raiding elephants

The raiding of crops by elephants is one of the major components of human-elephant conflict, causing loss of livelihood and retaliation against elephants. To mitigate this conflict, various intervention methods are in use by farmers across Africa and Asia; yet there have been few rigorous assessments of their effectiveness. We provide an assessment of the efficacy of interventions in use by communities in Assam from a 3-year survey dataset using Generalized Linear Mixed Modeling. We found spotlights, chili fences, and electric fences to be highly effective at preventing crop damage by elephants when used in isolation, but when used in combination with noise their efficacy was compromised. Our study highlights the importance of evaluating intervention methods to determine their effectiveness. We propose the use of fences and spotlights be promoted in Assam, in conjunction with long-term habitat protection and restoration strategies.

Phytotoxicity and Potential Allelopathy in Pale (Cynanchum rossicum) and Black swallowwort (C. nigrum)

AbstractThe introduced exotic vines pale and black swallowwort rapidly have become invasive throughout regions of the northeastern United States and adjoining areas of Canada. Preliminary studies have reported that the species are allelopathic, possibly contributing to their competitive ability and invasiveness. Results from our laboratory assays indicated that swallowwort root exudates caused significant root length reductions (e.g., 40% for butterfly milkweed and 20% for large crabgrass) and reduced germination (e.g., 25% for lettuce) of indicator species. Additional bioassays with dried swallowwort tissues demonstrated that tissue leachates caused varied responses in indicators, with both significant stimulatory and inhibitory effects. In particular, significant congeneric interactions were noted between the two swallowwort species. Evidence from this study of swallowwort tissue phytotoxicity has important implications for developing effective management and habitat restoration strategies for the two invasive species.

Between-Patch Bird Movements within a High-Andean Polylepis Woodland/Matrix Landscape: Implications for Habitat Restoration

The movement ability of species in fragmented landscapes must be considered if habitat restoration strategies are to allow maximum benefit in terms of increased or healthier wildlife populations. We studied movements of a range of bird species between woodland patches within a high-altitude Polylepis/matrix landscape in the Cordillera Vilcanota, Peru. Movement rates between Polylepis patches differed across guilds, with arboreal omnivores, arboreal sally-strikers and nectarivores displaying the highest movement rates, and understorey guilds and arboreal sally-gleaners the lowest movement rates. Birds tend to avoid flights to more distant neighboring patches, especially when moving from patches which were themselves isolated. The decline in bird flight frequencies with increasing patch isolation followed broken-stick models most closely, and while we suggest that there is evidence for a decline in between-patch movements over distances of 30–210 m, there was great variability in movement rates across individual patches. This variability is presumably a result of complex interactions between patch size, quality and configuration, and flight movement patterns of individual bird species. Our study does, however, highlight the contribution small woodland patches make toward fragmented Polylepis ecosystem functioning, and we suggest that, where financial resources permit, small patch restoration would be an important compliment to the restoration of larger woodland patches. Most important is that replanting takes place within 200 m or so of existing larger patches. This will be especially beneficial in allowing more frequent use of woodland elements within the landscape and in improving the total area of woodland patches that are functionally connected.

Prioritizing conservation targets in a rapidly urbanizing landscape

We used an optimization modeling framework to devise spatially explicit habitat acquisition and restoration strategies for 19 remnant-dependent butterflies in a rapidly urbanizing county in the Chicago area. We first identified the smallest sets of protected sites that would contain at least one population of each species, and two populations for species present in multiple sites. We then identified undeveloped properties contiguous with these sites whose acquisition would further enhance conditions for focal species. Next, we considered parcels in the surrounding landscape that could potentially be acquired and restored to provide additional habitat. Assuming that the conservation value of additional habitats would increase with their proximity to protected sites, we examined tradeoffs between distance to sites and the cost of acquisition and restoration. The tradeoff curves generated by the model represented choices among sets of reserves that varied widely with regard to cost and distance. Among the non-dominated solutions for a given total area budget, the best solutions depend on the decision makers preference for these two objectives. Sets along the frontier of these curves differed in total cost due to the variation in the number of wetlands per parcel, the number and cost of parcels that must be acquired to provide sufficient habitat, and restoration costs. Several parcels appeared in all solutions and should be prioritized for acquisition. Our general approach is readily adaptable to other locations and planning objectives, but the models would need to be modified to accommodate different target species and their habitat requirements.

Modeling Stream Network‐Scale Variation in Coho Salmon Overwinter Survival and Smolt Size

AbstractWe used multiple regression and hierarchical mixed‐effects models to examine spatial patterns of overwinter survival and size at smolting in juvenile coho salmon Oncorhynchus kisutch in relation to habitat attributes across an extensive stream network in southwestern Oregon over 3 years. Contributing basin area explained the majority of spatial variation (R2 = 0.57‐0.63) in coho salmon overwinter survival (range = 0.02‐0.63), with highest survival rates observed in smaller headwater and intermittent streams. Other habitat attributes, including proportional pool area, percent exposed bedrock substrate, percent broadleaf canopy cover, and adult salmon carcass density, were relatively poor predictors of survival. Indices of individual fish condition, including fall parr fork length, condition factor, and parasite infestation rates, were also relatively uninformative in coho salmon overwinter survival models. Coho salmon smolt length was primarily a function of length at the time of fall tagging, but stream type, contributing basin area (positive effect), thermal history (positive effect), and black spot infestation (i.e., trematode metacercariae; negative effect) were also important. The consistent, broad spatial gradients in overwinter survival observed in this study can help guide efforts designed to enhance coho salmon production in coastal streams and suggest that habitat protection, restoration, and enhancement strategies will be best guided by a whole‐basin context.

Identifying Conservation and Restoration Priorities for Saproxylic and Old-Growth Forest Species: A Case Study in Switzerland

Saproxylic (dead-wood-associated) and old-growth species are among the most threatened species in European forest ecosystems, as they are susceptible to intensive forest management. Identifying areas with particular relevant features of biodiversity is of prime concern when developing species conservation and habitat restoration strategies and in optimizing resource investments. We present an approach to identify regional conservation and restoration priorities even if knowledge on species distribution is weak, such as for saproxylic and old-growth species in Switzerland. Habitat suitability maps were modeled for an expert-based selection of 55 focal species, using an ecological niche factor analyses (ENFA). All the maps were then overlaid, in order to identify potential species' hotspots for different species groups of the 55 focal species (e.g., birds, fungi, red-listed species). We found that hotspots for various species groups did not correspond. Our results indicate that an approach based on "richness hotspots" may fail to conserve specific species groups. We hence recommend defining a biodiversity conservation strategy prior to implementing conservation/restoration efforts in specific regions. The conservation priority setting of the five biogeographical regions in Switzerland, however, did not differ when different hotspot definitions were applied. This observation emphasizes that the chosen method is robust. Since the ENFA needs only presence data, this species prediction method seems to be useful for any situation where the species distribution is poorly known and/or absence data are lacking. In order to identify priorities for either conservation or restoration efforts, we recommend a method based on presence data only, because absence data may reflect factors unrelated to species presence.

Influence of within‐patch habitat quality on high‐Andean Polylepis bird abundance

Habitat restoration strategies for fragmented high Andean forest landscapes must consider the influence of within‐patch habitat quality on bird abundance. I examined vegetation and bird abundance at three locations within a highly fragmented Polylepis forest landscape in the Cordillera Vilcanota, southern Peru. Across the landscape, there was significant variation in the vegetation structure of Polylepis forest patches of different size categories, especially in terms of tree girth, tree height, tree density, and canopy vegetation structure. Principal Component Analysis extracted five factors of habitat quality, which together accounted for 74.2% of the variability within 15 habitat variables. Polylepis bird species differed in their responses to habitat quality but, overall, variation in Polylepis bird abundance was not fully captured by the range of habitat quality variables. Tall, dense vegetation cover was clearly important for 11 conservation‐important species, a high density of large trees was important for 10 species and primary forest ground cover was important for eight species. Habitat quality exhibited no significant influence on the abundance of only one species –Asthenes urubambensis. The abundance of seven species was associated with lower elevation forest, but only one species was associated with higher elevation forest. Management of habitat quality in large and medium remnant forest patches throughout the Cordillera Vilcanota, particularly in the 3800–4200 m elevation range, will be a cornerstone in ensuring the persistence of the majority of conservation‐important bird species populations.

Benthic invertebrates investigation in the East River and habitat restoration strategies

The stream ecology of the East River is studied using benthic macro-invertebrates as indicator species. Samples were taken from 12 selected sites with different environmental conditions, from the upper reaches to the lower reaches. Four sites were selected to assess restoration strategies. The taxon richness, number density, biodiversity, and bio-community indices of benthic invertebrates remain at a relatively high level in the upper and middle reaches of the East River, but reduce to nearly zero in the lower reaches. The main ecological stresses are loss of habitat because of reclamation and the separation of riparian waters from the river. An important restoration strategy is to create multiple habitats with high habitat diversity, such as riparian lakes, wetlands, backwaters and sluggish flow zones, and to reconnect separated oxbow lakes with the river. Riparian waters should be managed in a similar way in Zengjiang Bay, allowing river flow to carry fine sediments into the riparian waters. Consequently, the fine sediment can deposit to form a mud layer. Fishes and invertebrates may live and spend parts of their life cycle in riparian waters. The Fengshuba Dam causes instantaneous fluctuation in flow discharge, and the aquatic ecology in the downstream reaches is impacted. A restoration strategy is required to adjust the operation scheme of the reservoir. Slope erosion and landslides also impact the stream ecology; the main restoration strategy for this is reforestation.

Large‐scale spatial and temporal dynamics of the vulnerable and highly mobile superb parrot

AbstractAim To investigate the spatial and temporal dynamics of the vulnerable and highly mobile superb parrot (Polytelis swainsonii) across its range in south‐eastern mainland Australia.Location South‐eastern Australia (27°–37° S latitude and 141°–151° E longitude).Methods We used generalized additive models (GAMs) to model time‐specific bird atlas occurrence data against time‐specific plant productivity data, plus a range of environmental predictor variables. We then examined the effects of environmental variables on the temporal and spatial patterns of predicted abundance and distribution of the superb parrot using a correlative mapping approach.Results Key findings from GAM analysis were: (1) there was a strong positive relationship between abundance and plant productivity in all regions, but (2) the response of abundance to other predictor variables often differed between regions. Correlative mapping predictions of the abundance and distribution of the superb parrot also indicated that: (1) predicted abundance varied through time and space, (2) predicted abundance sometimes decreased in all regions, but at other times some regions had high abundance when others had low, and (3) changes in plant productivity (and therefore climate) were associated with this variation.Main conclusion The superb parrot favours productive landscapes that are also favoured for agriculture. Movements appear to be associated with seasonal and year to year climate variability. Thus, variation in the recorded abundance of the superb parrot may mask population trends, suggesting that existing population estimates are unreliable. Also, high abundances in some areas, and at some times, may reflect deteriorating habitat conditions elsewhere rather than species recovery. Temporal variability in the distribution of the superb parrot makes it difficult to identify specific drought refugia. Consequently, through time, as key habitat continues to deteriorate, the species will become increasingly vulnerable and threatened. Whole‐landscape habitat conservation and restoration strategies are therefore needed to sustain superb parrot populations in the long‐term.

Impact of hydropattern disturbance on crayfish population dynamics in the seasonal wetlands of Everglades National Park, USA

Abstract1. The natural hydropattern in the seasonally‐flooded marl prairie wetlands of Everglades National Park has been severely disrupted by human water control activities, seriously impacting higher trophic organisms, e.g. wading birds, that depend on these wetlands. Less is known about the impacts on key aquatic fauna, such as crayfish Procambarus alleni, or how these populations might respond to proposed habitat restoration strategies. 2. Under severe environmental stress, populations of burrowing crayfish are predicted to have skewed size structure, low reproductive success, low survival, and widespread dispersal. As predicted for populations in stressed habitats, crayfish density was low, small dispersing adults were dominant, juvenile abundance was low, and survival was low in habitats where the hydroperiod (duration of flooding) was short and groundwater level was lowest.3. Crayfish dispersed during flooding, but during the drydown, they burrowed rather than sought deeper water. This dispersal strategy may be adaptive for surviving in seasonal wetlands, but this had severe consequences on survival in disturbed habitats with shortened hydroperiods. Survival in burrows during the dry season was high in the longer‐hydroperiod habitats but was zero in the short‐hydroperiod habitat where the groundwater level fell more than 1 m.4. Long‐hydroperiod marl prairie may function as sources, whereas short‐hydroperiod habitats act as population sinks. Our study suggests that the threshold conditions for preventing mass mortality of crayfish in these wetlands are hydroperiods >7 months and groundwater levels <0.5 m below the surface during the dry season.5. Historical (pre‐drainage) hydroperiods appear to be restricted to the longest hydroperiod areas of the marl prairie. This indicates that much of the marl prairie wetlands now function as population sinks for crayfish and other invertebrates. The historical hydropatterns need to be re‐established throughout the marl prairie wetlands to achieve the restoration goal of increasing productivity in the aquatic faunal community.Copyright © 2001 John Wiley & Sons, Ltd.

BEHAVIORAL MECHANISMS AND HABITAT USE BY BIRDS IN A FRAGMENTED AGRICULTURAL LANDSCAPE

Effective conservation and habitat restoration strategies in human-dominated landscapes must be based on an understanding of the ways that habitat loss and fragmen- tation affect native species. We studied avian foraging behavior and patterns of occurrence in the highly fragmented agricultural landscape of the Kellerberrin district of Western Australia to better understand the factors underlying species declines and losses. We con- ducted three surveys of 30 wandoo woodland patches that ranged in size from 1.3 to 101.3 ha. Some patches were part of larger remnants of native vegetation, ranging in size from 3.5 to 1204.8 ha and including other habitat types. We examined the extent to which patterns of species richness, the occurrence and composition of foraging guilds, and the occurrence of individual species varied with features of woodland patches, remnants, and the sur- rounding landscape. Using multiple regression analyses, the best model for species richness included terms for the log of remnant area, the patch diversity of each remnant, and woodland patch condition. We delineated eight foraging guilds based on similarities in the substrate/method dimension and also using multidimensional scaling analyses. The best model for the number of foraging guilds present in a patch included a single variable representing shrub density. Analyses of nestedness based on guilds and on individual species were both significant; and for the latter, 11 of 13 species made a significant contribution to the overall pattern. We derived separate models for the occurrence of each of eight species and one guild using multiple logistic regression. Significant models included, either separately or in combi- nation, the following variables: the log of remnant area, patch area, the total area of wood- land in a remnant, and the distance to other woodland patches. For four species that had sufficient records to examine shifts in foraging behavior, we observed significant differences in both foraging methods and substrates with changes in remnant size and/or the presence of other species or guilds. Our analyses indicated that remnant area was the best single variable for measures of community structure, in part because it was strongly correlated with other variables, such as total woodland area, patch area, remnant patch diversity, number of corridor connections, and measures of isolation. For foraging guilds and for individual species, variables other than remnant area assumed greater importance. The strong patterns of nestedness for for- aging guilds by remnant area may reflect the diminished availability of certain prey items in small, degraded remnants. This notion is reinforced by the relatively high species and guild richness recorded in small patches that were either fenced from grazing or embedded in large remnants. The nested pattern of species within some foraging guilds, however, indicates the importance of additional aspects of their ecology. A focus on richness alone may mask the unique responses of bird species to fragmentation and may divert attention from important considerations in the development of land-use policy and reserve acquisition.